1. Field of the Invention
The present invention relates to a developer loading method for loading a replenishment developer containing a toner and a carrier into a developer accommodating container and to a developer accommodating container into which the developer is loaded by the developer loading method. The present invention also relates to a developer replenishment device comprising the developer accommodating container and an image forming apparatus. Furthermore, the present invention relates to a method for manufacturing a loaded developer accommodating container that is loaded with a replenishment developer containing a toner and a carrier and to a method for supplying the developer from the loaded developer accommodating container into a development device.
2. Description of the Related Art
In a conventional image forming apparatus using a two-component developer containing a toner and a carrier, because the toner inside the development device is consumed, a replenishment toner accommodating unit is provided for accommodating a replenishment toner that is supplied to the development device.
Following a transition to full-color images in the image forming apparatuses, even higher image quality is now required, and the size of toner particles used in the image forming apparatus is decreased to meet such a requirement. Due to the decrease in size of toner particles, the surface area of the toner increases and the toner component is easily spent on the carrier. Further, as the size of the image forming apparatuses decreases and speed thereof increases, high speed rotation proceeds inside the development device with a small amount of developer. As a result, the stresses applied to the developer increase and the deterioration of carrier is readily accelerated by the removal of the carrier coating film and toner spent. With the developer using such deteriorated carrier, high-quality images are difficult to obtain even when the toner has a small particle size. In a configuration in which a replenishment toner is supplied to the development device, the replenishment toner is supplied, while the toner inside the development device is consumed by the development process. Therefore, the toner inside the development device is replaced, but the carrier inside the development device is not replaced. As a result, in order to inhibit the degradation of image quality caused by carrier deterioration it is necessary to replace frequently the developer inside the development device. However, frequent replacement of the developer inside the development device leads to the increased maintenance cost and rises the printout unit cost.
An image forming apparatus described in Japanese Examined Patent Application No. 60-18065 (Prior Art 1) is an example of a configuration in which the degradation of image quality caused by carrier deterioration inside the development device can be inhibited, while inhibiting the increase in maintenance cost. In the image forming apparatus described in Prior Art 1, a replenishment carrier is periodically and automatically supplied independently of the replenishment toner. Further, the carrier inside the development device is replaced by discharging the developer in an amount corresponding to that of the supplied replenishment carrier from the development device. As a result, the ratio of the deteriorated carrier in the entire carrier present in the development apparatus can be reduced and the degradation of image quality caused by carrier deterioration inside the development apparatus can be inhibited. Because the ratio of the deteriorated carrier in the entire carrier present in the development apparatus can be reduced, the replacement frequency of the developer inside the development device can be decreased and the increase in the maintenance cost can be inhibited.
However, in the configuration described in Prior Art 1, an accommodation unit that accommodates the replenishment carrier has to be provided separately from the replenishment toner accommodating unit that accommodates the replenishment toner, and a replenishment device has to be provided separately from the replenishment device that supplies the replenishment toner. As a result, the image forming apparatus is increased in size and cost thereof rises.
An image forming apparatus described in Japanese Unexamined Patent Application No. 2004-29306 (Prior Art 2) is another example of a configuration in which the degradation of image quality caused by carrier deterioration inside the development device can be inhibited, while inhibiting the increase in maintenance cost. The image forming apparatus described in Prior Art 2 comprises a developer accommodating container that accommodates a premix toner that is a developer obtained by mixing a replenishment carrier with a replenishment toner and having a toner concentration higher than that of the developer inside the development device, and this premix toner is supplied to the development device. Further, the replacement of carrier inside the development device is performed by discharging the developer in an amount corresponding to that of the supplied premix toner from the development device. In this image forming device, because the premix toner is supplied, it is not necessary to provide an accommodating container and a replenishment device for the replenishment toner and replenishment carrier. As a result, the increase inside and cost of the device can be inhibited with respect to those of the image forming apparatus of Prior Art 1.
On the other hand, Japanese Unexamined Patent Application No. 2004-323062 (Prior Art 3) describes a toner replenishment device that supplies a replenishment toner into a development device, wherein the replenishment toner located in the replenishment toner accommodating container is sucked in by a negative pressure created by a powder pump, and the replenishment toner that has been sucked in is conveyed into the development device. The toner replenishment device of Prior Art 3 comprises inside thereof a conveying path member through which the replenishment toner passes and a powder pump, and the replenishment toner located in the vicinity of the toner discharge port of the replenishment toner accommodating container is discharged from the toner discharge port by the negative pressure created by the suction force of the powder pump. The replenishment toner that has been discharged from the toner discharge port passes inside the conveying path member and is conveyed to the development device, whereby the replenishment toner is supplied to the development device. Further, when the replenishment toner located in the vicinity of the toner discharge port is discharged toward the development device by the negative pressure, the replenishment toner that is not located in the vicinity of the toner discharge port is moved toward the toner discharge port by the discharge of the toner located in the vicinity of the toner discharge port to the outside. With such toner replenishment device, the discharge of replenishment toner and the movement of replenishment toner inside the toner accommodating body are performed by the suction action of the powder pump. As a result, a toner conveying member serving to move the replenishment toner into the toner accommodating body becomes unnecessary.
As described hereinabove, in the image forming apparatus of Prior Art 3, the replenishment toner is accommodated in the toner accommodating container, and the replenishment toner is supplied into the development device by the toner replenishment device comprising a powder pump. The results of the comprehensive study conducted by the inventors demonstrated that a developer containing a toner and a carrier, as in the developer accommodating container described in Prior Art 2, can be accommodated in the toner accommodating container of the image forming apparatus described in Prior Art 3, and this developer can be supplied to the development device by the negative pressure of a powder pump.
Further, the test performed by the six inventors of the present invention demonstrated that the following drawbacks are associated with the configuration in which a developer is supplied to the development device by the negative pressure of a powder pump. Thus, with a developer containing a toner and a carrier, the developer can be conveyed by the negative pressure of a powder pump, but when the carrier alone is conveyed, the conveyance with the powder pump stops. Where the conveyance of the carrier with the powder pump stops, the carrier clogs the conveying path member and cannot be moved even by the application of negative pressure.
As described above, in the toner accommodating container of Prior Art 3, no toner conveying member is required for transferring the replenishment toner into the toner accommodating body. Therefore, the toner accommodating container is not provided with the toner conveying member. Further, where the developer accommodating container is obtained by accommodating a developer inside an accommodating container identical to the toner accommodating container, the developer accommodating container does not contain a developer conveying member for conveying the developer inside the developer accommodating body. Where such a developer accommodating container is set into a developer replenishment device, because no developer conveying member is provided inside the developer accommodating body, the developer inside the developer accommodating body practically does not move within the interval after the developer accommodating container has been set and before the replenishment of the developer is started. Therefore, depending on a developer loading method, the carrier can be unevenly distributed inside the developer accommodating container and it is possible that the carrier alone will be discharged from the developer discharge port of the developer accommodating container when the developer supply is started.
Further, where the carrier alone is discharged from the developer discharge port, the carrier alone is conveyed by the powder pump, and the conveyance of the developer by the powder pump is stopped. On the other hand, where the developer containing the carrier and toner or the toner alone is discharged from the developer discharge port, the developer can be continuously conveyed by the powder pump.
Even with the developer accommodating container containing no developer conveying member inside the developer accommodating body, the developer is moved inside the developer accommodating container by discharging the developer from the developer discharge port. Due to loading of the developer, the carrier is non-uniformly distributed inside the developer container and even the carrier that has not come into contact with the toner is gradually brought into contact with the toner by the movement of the developer inside the developer accommodating container. Further, because the carrier that has once come into contact with the toner can hardly assume again a state in which it has no contact with the toner, when the carrier is discharged from the developer discharge port, the carrier is discharged in a mixture with the toner. Therefore, if the carrier alone is not discharged when the replenishment is started, even if a region in which only the carrier is present exists inside the developer accommodating container, no serious problem is associated therewith.
However, before the replenishment is started, the movement of the developer inside the developer accommodating container that accompanies the discharge of the developer is not performed. Therefore, in a loading state in which the carrier alone is discharged when the replenishment is started, the operation of conveying the developer with the powder pump is stopped, as described hereinabove.
Technologies relating to the present invention are also disclosed in, e.g., Japanese Patent Application No. 2004-15276.